A conventional portable telephone has an antenna for communicating to a cellular base station by way of radio signals. The antenna is typically a half-wave dipole antenna mounted on the exterior of the portable telephone. The length of the half-wave or quarter-wave dipole being dictated by the operating radio-frequency. For example, a portable telephone operating in the 800 to 900 MHz frequency range has a half-wave dipole approximately 85 mm in length. The half-wave size dipole antenna can effectively be decreased by winding the element around a structurally stable core to reduce the relative size of the antenna with respect to the portable telephone body.
Another antenna configuration includes two or more antenna resonators parasitically coupled together and oriented parallel to one another. Each parallel antenna resonator being anchored conductively to a shielding housing while the other end serves as a free resonator. Thus, antenna elements are configured to form "inverted-F or -L antennas" as detailed in U.S. Pat. No. 5,365,246 as well as the references cited therein.
While prior art linear antennas extending from either the side or top portions of a telephone housing and parallel to the long axis of a portable telephone achieve considerable signal gain, as do the inverted-F and -L antennas, there is a growing concern that the electromagnetic radiation emanating from portable telephones and associated antennas may have deleterious effects on neural function and health.
The increasing availability of portable telephones as well as the close contact of the telephone and associated antenna with an individual's head exacerbate these concerns. Considerable dosimetry over prolonged periods of time results owing to the proximity to the head and the regular exposure to electromagnetic radiation associated with portable telephones.
Since electromagnetic radiation intensity decreases as the reciprocal square of distance from the emanation source, antennas have been devised which can be swung into a position away from the portable telephone earpiece to a position nonparallel with the primary axis of the portable telephone. U.S. Pat. Nos. 5,777,261; 5,590,416 and PCT Publication WO 98/09342 are examples thereof. While these antennas serve to reduce electromagnetic radiation exposure to the head of a user by extending the antenna away from a user head, this is achieved by an antenna having at least two antenna positions. Typically, these antennas rotate or fold proximal to the portable telephone housing as an inactive position and rotate away from the user head and non-parallel to the primary axis of the portable telephone body in an active position. Such antennas have a limited operational lifetime owing to the regular stresses placed on the pivot about which the antenna position is varied. Thus, there exists a need for an antenna which reduces electromagnetic radiation exposure to a user's head through a permanently bent antenna.